How to Use a Multimeter to Test a Smartphone Motherboard

Updated on: December 6, 2018


This tutorial will reveal you just how to make use of a digital multimeter (DMM), an indispensable tool that you can utilize to identify circuits, discover other individuals’s electronic styles, and also test a smartphone motherboard. Hence the ‘multi’-‘meter’ or numerous measurement name.

One of the most standard points we measure are voltage and current. A multimeter is additionally great for some basic sanity checks as well as troubleshooting. Is your circuit not functioning? Does the button job? Put a meter on it! The multimeter is your first defence when fixing a system. In this tutorial we will cover measuring voltage, current, resistance and continuity.

Every fixer must understand their method around a multimeter, which has just north of a zillion makes use of for testing electronic parts and also circuits.

In this tutorial we’re going to reveal you just how to utilize a multimeter. This tutorial is primarily attended to for beginners that are starting in electronic devices and also have no idea exactly how to use a multimeter and also how it can be useful. We’ll discover one of the most usual features on a multimeter as well as exactly how to measure current, voltage, resistance as well as exactly how to check continuity.

What is a multimeter as well as why do you require one?

A multimeter is a measurement tool definitely necessary in electronic devices. It integrates three important attributes: a voltmeter, ohmeter, and ammeter, as well as in some cases continuity.

The tool permits you to comprehend what is taking place in your circuits. Whenever something in your circuit isn’t functioning, it will assist you troubleshooting. Here’s some circumstances in electronic devices tasks that you’ll find the multimeter helpful:

  • is the button activate?
  • is this wire conducting the electricity or is it damaged?
  • exactly how much current is moving via this led?
  • just how much power do you have left on your batteries?

What would multimeters measure?

Nearly all multimeters can measure voltage, current, and also resistance.

Some multimeters have a continuity check, causing a loud beep if 2 things are electrically linked. This is helpful if, for circumstances, you are constructing a circuit and also connecting wires or soldering; the beep suggests everything is linked and also absolutely nothing has actually come loose. You can likewise use it to ensure 2 points are not attached, to aid protect against brief circuits.

A number of multimeters additionally have a diode check feature. A diode resembles a one-way shutoff that only allows electrical energy flow in one instructions. The specific feature of the diode check can differ from one type to another. If you’re dealing with a diode and can not tell which means it enters the circuit, or if you’re not sure the diode is functioning correctly, the check feature can be quite helpful. If your DMM has a diode check feature, read the guidebook to learn exactly how it functions.

Advanced models might have other features, such as the ability to measure and also determine various other electric parts, like transistors or capacitors. Considering that not all other multimeters have these features, we will not cover them in this tutorial. You can review your multimeter’s handbook if you need to use these attributes.

What Do All the Symbols Mean?

There’s a lot going on when you check out the selection knob, yet if you’re just mosting likely to be doing some fundamental stuff, you won’t also make use of fifty percent of all the settings. In any kind of instance, here’s a rundown of what each sign implies:

Direct Current Voltage (DCV):In some cases it will certainly be signified with a V– rather. This setup is made use of to measure straight current (DC) voltage in things like batteries.
Alternating Current Voltage (ACV): Sometimes it will certainly be represented with a V ~ rather. This setting is used to measure the voltage from alternating current sources, which is practically anything that plugs right into an outlet, along with the power coming from the outlet itself.
Resistance (Ω): This determines just how much resistance there remains in the circuit. The lower the number, the less complicated it is for the current to move through, as well as the other way around.
Continuity: Usually represented by a wave or diode sign. This merely examines whether or not a circuit is complete by sending a very percentage of current via the circuit as well as seeing if it makes it out the other end. Otherwise, after that there’s something along the circuit that’s creating a problem– discover it!
Straight Current Amperage (DCA): Similar to DCV, but instead of providing you a voltage reading, it will tell you the amperage.
Straight Current Gain (hFE): This setup is to evaluate transistors and their DC gain, yet it’s mostly worthless, because the majority of electricians and also enthusiasts will certainly make use of the continuity check rather.

Your multimeter might also have a dedicated setup for testing the amperage of AA, AAA, as well as 9V batteries. This setup is normally denoted with the battery icon.

Once again, you probably will not also use fifty percent of the settings shown, so don’t get bewildered if you only know what a few of them do.

Just how to Utilize a Multimeter

For beginners, allow’s look at a few of the different parts of a multimeter. At the really standard level you have the device itself, along with two probes, which are the black and also red cables that have plugs on one end as well as metal tips on the other.

The tool itself has a screen at the top, which gives you your readout, and also there’s a huge selection knob that you can rotate around to pick a particular setup. Each setting might likewise have various number worths, which are there to measure different strengths of voltages, resistances, and also amps. So if you have your multimeter collection to 20 in the DCV section, it will certainly measure voltages as much as 20 volts.

Your DMM will certainly also come with 2 or three ports for plugging in the probes:

  • COM port stands for “Common”, and also the black probe will constantly connect into this port.
  • the VΩmA port (sometimes denoted as mAVΩ) is just a phrase for voltage, resistance, and also current (in milliamps). This is where the red probe will certainly link into if you’re measuring voltage, resistance, continuity, and current less than 200mA.
  • the 10ADC port (occasionally signified as simply 10A) is utilized whenever you’re measuring current that’s greater than 200mA. If you’re not sure of the current draw, begin with this port. On the various other hand, you would not utilize this port whatsoever if you’re measuring anything aside from current.

Warning: Make certain that if you’re measuring anything with a current greater than 200mA, you connect the red probe right into the 10A port, as opposed to the 200mA port. Or else you can blow the fuse that’s inside of the multimeter. Moreover, measuring anything over 10 amps could blow a fuse or destroy the multimeters also.

Your measurement tool could have totally separate ports for measuring amps, while the other port is specifically just for voltage, resistance, and also continuity, however the majority of less costly multimeters will share ports.

Anyway, let’s start really making use of a multimeter. We’ll be measuring the voltage of a AA battery, the current draw of a wall surface clock, and the continuity of an easy wire as some instances to obtain you began as well as knowledgeable about utilizing a multimeter.

Parts of a Multimeter

Multimeters have four components:

  • Display: this particular is where the dimensions are shown
  • Selection Knob: this picks what you wish to measure
  • Ports: this is where you plug in the probes
  • Probes: a multimeter features two probes. Typically, one is red and also the various other is black.
Read Also:  Basic Digital Multimeter Reviews 2019


  • “COM” or “–” port is where the black probe should be linked. The COM probe is traditionally black.
  • 10A is utilized when measuring large currents, higher than 200mA.
  • µAmA is utilized to measure current.
  • allows you to measure voltage and resistance as well as examination continuity.


COM mean usual as well as is often linked to Ground or ‘-‘ of a circuit.The COM probe is conventionally black yet there is no distinction between the red probe and black probe other than shade.


10A is the special port used when measuring big currents (higher than 200mA).

Selection Knob

The selection knob permits the user to set the tool to review different points such as milliamps (mA) of current, voltage (V) and also resistance (Ω).


2 probes are plugged right into 2 of the ports on the front of the system. The probes have a banana kind port on the end that links into the multimeter. Any kind of probe with a banana plug will deal with this meter. This enables various types of probes to be made use of.

Probe Types

There are various kinds of probes readily available. Here are a few of our faves:

  • Banana to Alligator Clips: These are terrific cords for attaching to big cables or pins on a breadboard. Good for doing longer term tests where you do not have to need to hold the probes in location while you adjust a circuit.
  • Banana to IC Hook: IC hooks function well on smaller sized ICs and legs of ICs.
  • Banana to Tweezers: Tweezers come in handy if you are requiring to evaluate SMD elements.
  • Banana to Test Probes: If you ever before damage a probe, they are economical to change!

Measuring Voltage

To begin, allow’s measure voltage on a AA battery: Plug the black probe into COM and also the red probe into mAVΩ. Establish to “2V” in the DC (straight current) array. Virtually all mobile electronics use straight current), not alternating current. Link the black probe to the battery’s ground or ‘-‘ and also the red probe to power or ‘+’. Press the probes with a little stress against the favorable and adverse terminals of the AA battery. If you’ve got a fresh battery, you ought to see around 1.5 V on the display (this battery is brand name brand-new, so its voltage is slightly greater than 1.5 V).

You can possibly measure DC voltage or AC voltage. The V with a straight line means DC voltage. The V with the bumpy line means AC voltage.

To measure voltage:

  1. Set the mode to V with a curly line if you’re measuring AC voltage or to the V with a straight line if you’re measuring DC voltage.
  2. Make sure the red probe is attached to the port with a V beside it.
  3. Connect the red probe to the positive side of your component, which is where the current is coming from.
  4. Link the COM probe to the opposite side of your component.
  5. Review the value on the screen.

Idea: to measure voltage you have to attach your multimeter in parallel with the component you intend to measure the voltage. Positioning the multimeter in parallel is putting each probe along the leads of the component you wish to measure the voltage.

Measuring a battery’s voltage

In this instance we’re going to measure the voltage of a 1.5 V battery. You recognize that you’ll have around 1.5 V. So, you should choose a variety with the selection knob that can check out the 1.5 V. So you should select 2V in the instance of this multimeter. If you have an autorange one, you do not have to worry regarding the variety you require to pick.

Begin by turning on it, connecting the probes into their corresponding ports and after that setting the selection knob to the highest number worth in the DCV section, which in my instance is 500 volts. If you do not recognize at the very least the voltage array of the important things you’re measuring, it’s constantly an excellent suggestion to begin with the highest value first as well as then function your method down until you get an exact reading.

In this case, we understand the AA battery has a really low voltage, yet we’ll start at 200 volts just for the sake of example. Next, position the black probe on the unfavorable end of the battery and the red probe on the positive end. Take a look at the reading on the screen. Since we have the multimeter collection to a high 200 volts, it reveals “1.6” on the display, implying 1.6 volts.

However, I want an even more precise reading, so I’ll move the selection knob reduced to 20 volts. Right here, you can see that we have an even more exact reading that floats in between 1.60 as well as 1.61 volts. If you were to ever set the selection knob to a number value less than the voltage of the important things you’re testing, the multimeter would simply check out “1”, indicating that it’s overwhelmed. So if I were to set the handle to 200 millivolts (0.2 volts), the 1.6 volts of the AA battery is excessive for the multimeter to handle at that setting.

In any type of situation, you could be asking why you would certainly require to check the voltage of something in the first area. Well, in this case with the AA battery, we’re inspecting to see if it has any kind of juice left. At 1.6 volts, that’s a fully-loaded battery. Nonetheless, if it were to read 1.2 volts, it’s close to being pointless.
In a more functional circumstance, you might do this kind of measuring on an automobile battery to see if it could be passing away or if the generator (which is what bills the battery) is going poor. A reading between 12.4-12.7 volts indicates that the battery is in excellent form. Anything reduced and that’s evidence of a dying battery. Furthermore, begin your automobile up and also rev it up a bit. If the voltage does not increase to around 14 volts or so, after that it’s most likely that the generator is having concerns.


What happens if you choose a voltage setting that is also low for the voltage you’re attempting to measure? Absolutely nothing poor. The meter will merely display a 1. This is the meter attempting to inform you that it is overloaded or out-of-range. Whatever you’re attempting to read is excessive for that specific setting. Try transforming the multimeter knob to a the next greatest setting.

Selection Knob

Just why does the meter knob read 20V and not 10V? If you’re seeking to measure a voltage much less than 20V, you turn to the 20V setup. This will certainly allow you to check out from 2.00 to 19.99. The first digit on several multimeters is just able to present a ‘1’ so the varieties are restricted to 19.99 as opposed to 99.99. For this reason the 20V max array rather than 99V max range.

Measuring Resistance

Connect the red probe into the ideal port as well as turn the selection knob to the resistance area. Then, attach the probes to the resistor leads. The way you attach the leads does not matter, the outcome is the exact same.

Normal resistors have color codes on them. If you do not know what they imply, that’s ok! There are lots of on the internet calculators that are very easy to use. Nonetheless, if you ever before find yourself without net accessibility, a multimeter is really helpful at measuring resistance.

Pick an arbitrary resistor as well as established the multimeter to the 20kΩ setup. After that hold the probes against the resistor legs with the same quantity of stress you when pressing a key on a key-board.

Read Also:  How to Use a Craftsman Digital Multimeter

The meter will certainly check out one of three points, 0.00, 1, or the real resistor value.

In this case, the meter reviews 0.97, suggesting this resistor has a value of 970Ω, or regarding 1kΩ (remember you remain in the 20kΩ or 20,000 Ohm mode so you need to relocate the decimal 3 places to the right or 970 Ohms).

If the multimeter reads 1 or displays OL, it’s strained. You will require to attempt a higher setting such as 200kΩ mode or 2MΩ (megaohm) mode. There is no injury if this take place, it simply indicates the array handle requires to be readjusted.

When the multimeter checks out 0.00 or nearly zero, after that you need to decrease the setting to 2kΩ or 200Ω.

Keep in mind that many resistors have a 5% resistance. This suggests that the shade codes may suggest 10,000 Ohms (10kΩ), yet due to the fact that of disparities in the production process a 10kΩ resistor could be as reduced as 9.5 kΩ or as high as 10.5 kΩ. Don’t stress, it’ll work just great as a pull-up or general resistor.

Generally of thumb, it’s unusual to see a resistor less than 1 Ohm. Keep in mind that measuring resistance is not excellent. Temperature can influence the reviewing a great deal. Additionally, measuring resistance of a gadget while it is literally mounted in a circuit can be really challenging. The surrounding parts on a circuit card can substantially influence the analysis.

The mockup normally looks like with a standard clock running off of a AA battery. On the silver lining, the cord going from the battery to the clock is separated. We merely position our 2 probes in between that break to complete the circuit again (with the red probe linked to the power source), only this time around our multimeter will read out the amps that the clock is pulling, which in this instance is around 0.08 mA.

While a lot of multimeters can likewise measure alternating current (AC), it’s not really a great idea (particularly if its live power), because AC can be hazardous if you wind up making a mistake. If you require to see whether an outlet is working, use a non-contact tester rather.

To measure current you require to birth in mind that elements in collection share a current. So, you require to attach your multimeter in collection with your circuit.

TIP: to put the multimeter in collection, you require to place the red probe on the lead of a component and the black probe on the next component lead. The multimeter acts as if it was a cord in your circuit. If you disconnect the multimeter, your circuit will not work.

Prior to measuring the current, make certain that you’ve connected in the red probe in the ideal port, in this case µAmA. In the example listed below, the same circuit of the previous instance is utilized. The multimeter is part of the circuit.

Tests Continuity

If there is very low resistance in between two factors, which is less than a couple of ohms, the two factors are electrically connected as well as you’ll hear a continuous sound. If the audio isn’t constant or if you do not hear any type of sound in all, it means that what you’re testing has a malfunctioning link or isn’t connected at all.

CAUTION: In order to examine continuity you must shut off the system! Turn off the power source.

Touch the two probes with each other as well as, as they are linked, you’ll listen to a constant sound.To test the continuity of a cable, you simply need to link each probe to the wire pointers.

Continuity is a wonderful way to examine if two SMD pins are touching. If your eyes can not see it, the multimeter is usually a great second testing source. When a system is not working, continuity is one more point to help troubleshoot the system.

  • Set your multimeter to the continuity setting making use of the selection knob.
  • The readout on the screen will quickly check out “1”, which means that there isn’t any continuity. This would certainly be proper given that we haven’t attached the probes to anything yet.
  • Next, make certain the circuit is unplugged as well as has no power. After that link one probe to one end of the wire as well as the various other probe to the other end– it matters not which probe goes on which end. If there is a complete circuit, your multimeter will either beep, show a “0”, or something besides a “1”. If it still reveals a “1”, then there’s a problem and your circuit isn’t total.
  • You can also evaluate that the continuity function services your multimeter by touching both probes to each other. This completes the circuit and also your multimeter need to let you recognize that.

A continuity test tells us whether 2 points are electrically connected: if something is continual, an electrical current can stream openly from one end to the other.

If there’s no continuity, it indicates there is a break somewhere in the circuit. This could show anything from a blown fuse or bad solder joint to an incorrectly wired circuit.

Altering the Fuse

Among the most typical blunders with a new multimeter is to measure current on a bread board by penetrating from VCC to GND. This will immediately brief power to ground through the multimeter triggering the bread board power supply to brown out. As the current hurries via the multimeter, the interior fuse will certainly warm up and afterwards stress out as 200mA streams with it. It will certainly take place in an instant as well as with no actual distinct or physical sign that something is incorrect.

Bear in mind that measuring current is done in collection (disrupt the VCC line to the breadboard or microcontroller to measure current). If you attempt to measure the current with a blown fuse, you’ll possibly notice that the meter checks out ‘0.00’ which the system doesn’t switch on like it should when you affix the multimeter. This is since the internal fuse is broken and also serves as a busted wire or open.

To change the fuse, discover your convenient dandy mini screw driver, as well as start securing screws. The elements and also PCB traces inside the multimeter are made to take various amounts of current. You will damage as well as possibly destroy your multimeter if you accidentally push 5A via the 200mA port.

There are times where you need to measure high current devices like an electric motor or heating element. Do you see the two locations to place the red probe on the front of the multimeter? 10A on the left as well as mAVΩ on the right? If you attempt to measure even more than 200mA on the mAVΩ port you risk of blowing the fuse. However if you use the 10A port to measure current, you run a much lower threat of blowing the fuse. The compromise is level of sensitivity. As we talked about above, by utilizing the 10A port and knob setup, you will just have the ability to review to 0.01 A or 10mA. A lot of systems utilize greater than 10mA so the 10A setup and port functions all right. If you’re trying to measure extremely low power (micro or nano amps) the 200mA port with the 2mA, 200uA, or 20uA can be what you need.


You’re now all set to use your digital multimeter to start measuring the world around you. Do not hesitate to start using it to respond to many questions. A digital multimeter will answer several questions regarding electronics.

A multimeter is a vital tool in any electronic devices laboratory. In this guide, we’ve shown you How To Use a Multimeter. You’ve found out just how to measure voltage, current as well as resistance, and also how to inspect continuity.